Dell have installed a Trusted root certificate on a lot of Laptops. This is a security risk as it means a bad actor could use this to strip away any SSL/HTTPS encryption of your site in certain circumstances.
Dell have admitted to this and provided instructions on how to delete it.
The instruction are here.
I have just followed them on an XPS13 (Jan 15) and they worked as described.
Dell have admitted to this and provided instructions on how to delete it.

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The instruction are here.
I have just followed them on an XPS13 (Jan 15) and they worked as described.